MEL Deferrals

A Minimum Equipment List (MEL) deferral allows an aircraft to continue operating with certain equipment inoperative, subject to specific conditions and time limits. PlaneConnection tracks MEL deferrals as part of the discrepancy management system, linking them to aircraft records, dispatch decisions, and maintenance workflows.

MEL Deferral Statuses

Each discrepancy record that involves an MEL deferral carries its own status tracking the resolution lifecycle.

Status	API Value	Dispatch Impact	Description
Open	`open`	Evaluated per flight	Discrepancy has been reported but no deferral decision has been made. The item must be evaluated before each flight.
Deferred	`deferred`	Conditionally dispatchable	Item has been deferred under the MEL with a specific category and time limit. Aircraft may dispatch subject to MEL conditions.
In Progress	`in_progress`	Depends on work scope	Corrective action is underway. The aircraft may or may not be available depending on the nature of the repair.
Resolved	`resolved`	No impact	Item has been repaired, tested, and returned to service. No further dispatch restrictions.

Deferral Lifecycle

MEL Categories

The FAA defines four MEL deferral categories (A through D), each with a specific repair interval. PlaneConnection tracks the category to calculate the deferral expiration date and trigger alerts.

Category	Repair Interval	Description
A	As specified in MEL	Items that must be repaired within the time frame specified in the MEL entry. Typically the most time-critical deferrals.
B	3 consecutive calendar days	Items that must be repaired within 3 calendar days (excluding the day of discovery).
C	10 consecutive calendar days	Items that must be repaired within 10 calendar days (excluding the day of discovery).
D	120 consecutive calendar days	Items that must be repaired within 120 calendar days (excluding the day of discovery). Least urgent deferrals.

Deferral intervals are measured in consecutive calendar days, not flight days or business days. The day the discrepancy is discovered does not count toward the interval. If a Category B item is deferred on Monday, it must be repaired by end of day Thursday.

Regulatory Basis

MEL deferrals are governed by several Federal Aviation Regulations:

Regulation	Requirement
14 CFR 91.213	Establishes when an aircraft may be operated with inoperative instruments and equipment. References the operator’s approved MEL.
14 CFR 135.179	Requires Part 135 operators to have an approved MEL. Specifies that the MEL must be based on the Master MEL (MMEL) for the aircraft type.
14 CFR 91.403	Owner/operator responsibility for maintaining the aircraft in airworthy condition.
MMEL / MEL Policy Letter 25	FAA guidance on MEL revision and amendment procedures.

PlaneConnection does not replace the operator’s approved MEL document. The system tracks deferral records and expiration dates to support dispatch decisions. Always refer to the approved MEL for specific deferral conditions, placards, and operating procedures (O) and maintenance (M) procedures.

Discrepancy Record Fields

Each MEL deferral is tracked as a discrepancy record with additional MEL-specific fields:

Field	Type	Required	Description
`title`	String	Yes	Short description of the discrepancy (e.g., “Left cabin door seal leaking”).
`ata_chapter`	String	No	ATA 100 chapter code (e.g., “52 — Doors”).
`description`	Text	Yes	Detailed description of the discrepancy.
`severity`	Enum	Yes	Severity level: `minor`, `major`, `critical`, `grounding`.
`status`	Enum	Auto	Current lifecycle status: `open`, `deferred`, `in_progress`, `resolved`.
`mel_category`	Enum	Conditional	MEL category (A, B, C, or D). Required when status is `deferred`.
`mel_certificate_number`	String	No	MEL certificate or reference number for the deferral.
`deferred_date`	Date	Conditional	Date the item was deferred. Required when status is `deferred`.
`ground_aircraft`	Boolean	No	Whether this discrepancy grounds the aircraft (prevents dispatch).
`resolution`	Text	Conditional	Description of the corrective action taken. Required when status is `resolved`.
`resolved_by`	String	Conditional	Person who performed the repair. Required when status is `resolved`.
`resolved_date`	Date	Conditional	Date the item was resolved. Required when status is `resolved`.
`work_order_ref`	String	No	Reference to an external work order or maintenance tracking number.

Severity Levels

Severity	Description	Dispatch Impact
Minor	Cosmetic or convenience item. Does not affect airworthiness.	Dispatch normally with notation.
Major	Affects aircraft capability but can be deferred under MEL.	Dispatch with MEL conditions applied.
Critical	Significant impact on aircraft systems. May require operational limitations.	Dispatch only with chief pilot or DO approval.
Grounding	Aircraft is not airworthy. Cannot be deferred.	Aircraft grounded until resolved.

Corrective Actions

Each discrepancy can have multiple corrective action records tracking the resolution steps:

Field	Type	Description
`description`	Text	Description of the corrective action step.
`assigned_to`	String	Person or vendor assigned to perform the action.
`status`	Enum	Action status: `pending`, `in_progress`, `completed`.
`completed_at`	Timestamp	When the corrective action was completed.
`completed_by`	String	Person who completed the action.

Manage MEL Deferrals

Step-by-step guide to creating and resolving MEL deferrals.

Aircraft Statuses

How aircraft status interacts with deferral dispatch decisions.

Manage Discrepancies

General discrepancy tracking and squawk management.

Track Due Items

Maintenance due-item tracking and scheduling.

SMS Reference

SmartScore

Operations Reference

FBO Reference

Maintenance Reference

Operational Reports

Portal Reference

Platform Reference

API Reference

MEL Deferral Statuses

Deferral Lifecycle

MEL Categories

Regulatory Basis

Discrepancy Record Fields

Severity Levels

Corrective Actions

Manage MEL Deferrals

Aircraft Statuses

Manage Discrepancies

Track Due Items

​MEL Deferral Statuses

​Deferral Lifecycle

​MEL Categories

​Regulatory Basis

​Discrepancy Record Fields

​Severity Levels

​Corrective Actions

​Related

Manage MEL Deferrals

Aircraft Statuses

Manage Discrepancies

Track Due Items

MEL Deferral Statuses

Deferral Lifecycle

MEL Categories

Regulatory Basis

Discrepancy Record Fields

Severity Levels

Corrective Actions

Related